Captopril is an angiotensin converting enzyme (ACE) inhibitor. It blocks a chemical that tightens blood vessels. This makes blood vessels relax, which lowers blood pressure and allows more blood and oxygen to get to your heart and other organs.

Zestril (Lisinopril) is an angiotensin converting enzyme (ACE) inhibitor. It blocks a chemical that tightens blood vessels. This makes blood vessels relax, which lowers blood pressure and allows more blood and oxygen to get to your heart and other organs.